The main objective of the proposed project is to test a developmental model of adolescent substance use that extends current psychosocial interaction models of usage. It incorporates a key aspect of adolescent development , the role of adolescent individuation. The proposed model hypothesizes causal sequences between variables that affect individuation and subsequently usage, both directly and indirectly. The model will be applied separately to three ethnic groups, Black, Mexican-American and Anglo, with the expectation that ethnic differences in individuation and family dynamics will have unique bearing on the role of individuation in substance use. Study 1 addresses measurement issues with questionnaires administered to the three ethnic groups. The first year of the study will be devoted to the assessment of 1050 adolescents and adults to develop triethnic comparability of measurement. Study 2 will use a cross- sequential longitudinal design and structural equation modeling to assess progression of adolescent substance use along with the adolescent individuation process. To maximize the number of years that cross- sectional and longitudinal data will be available, 6th, 7th, and 8th graders in three ethnic groups (n=6300) will be surveyed annually for three successive years, yielding data samples large enough for LISREL analyses. An additional purpose of the study is to determine how psychosocial variables impact the process of individuation in its effects on adolescent substance use. In this context, sociodemographic status, family atmosphere and parental relations will be investigated.